Engine



:e 27 1942. C, F, BACHLE 2,270,990

ENGINE Filed Jan. 25. 1940 2 sheets-sheet 1 Ja 19 15 J9 Z7 @i Y s:

` 4 @L Z6 zg Z Z 24 ZZ K- 2z Z3 u' "ZM Il' K r o Z Z7 gg Z5 i J' v ,A H 15 \\/\\.`I 14' l Z6 INVENTO Z7 ATTORNE Jan. 27, 1942.

c. F. BACHLE 2,270,990

ENGINE Filed Jan. 25, 1940 2 Sheets-Sheet Z c Y/ 1a jg ZZ Z3 INVENTOR.

BY hr2 i dak *d ZO 9 ATTORN Patented Jan. 27, 1942 UNITED STATES PATENT OFFICE ENGINE YCarl F. Bachle, Grosse Pointe, Mich., assignor, by mesne assignments, to Reconstruction Finance Corporation, Detroit, Mich.

Application January 25, 1940, Serial No. 315,531

3 claims. (01."123-171) This invention relates to engines and more. particularly to the cylinder head structure of an air cooled aircraft engine and more particularly to an improved construction for dissipating heat from the exhaust valve guide carried by the cylinder head and also for dissipating heat from certain critical portions of the cylinder head structure.

It has been observed that it is more difcult to cool an in-line air cooled engine than the radial type of engine. It is more di'icult to control the ow of air around the cylinder head and therefore it has not been desirable to build air cooled in-line aircraft engines except for those engines of relatively low power output. It has been found possible however, to improve the cooling of low powered output aircraft engines by providing means circulating the cooling air in closer relation with respect to the combustion chamber and the engine valves.

An object of the present invention is to provide for improved engine performance by providing an improved arrangement for dissipating heat from thev cylinder head structure.

A further object of the present invention is to improve engine operating characteristics by providing an air tunnel extending between the engine valves in close proximity to the combustion chamber, and by incorporating therewith an arrangement of cooling fins providing a maximum of area for the dissipation of heat, and more particularly it will be observed that this air tunnel` extends intermediate the rocker box and the combustion chamber.

More particularly, the objects of the present invention are best accomplished by providing an air tunnel whose total area in cross-section relative to the cylinder bore area is such as to pro- `vide a maximum of heat dissipation, and more particularly I provide a construction in which a plurality of cooling fins extend inwardly of said air tunnel directly from the hottest stressed portion of the cylinder head overlying the engine combustion chamber adjacent to the cylinder axis. Also, this present construction provides adequate cooling for the exhaust valve guide and substantially prevents distortion of the valve seats under the, influence of heat originating in the combustion chamber.

For a more detailed understanding of the invention, reference may be had to the accompanying drawings illustrating preferred embodiments of the invention, and in which;

Fig. 1 is a fragmentary sectional view through an engine cylinder and head structure taken subt5 stantially in a plane containing the axes of the intake and exhaust valves,

Fig. 2 is a fragmentary sectional view taken on the line 2-2 of Fig. 1,

Fig. 3 is a plan elevational View of a small power output aircraft engine, and

Fig. 4 is a sectional view through the engine cylinder illustrating a modified construction.

The engine illustrated in Figs. 1 and 2, and on which the present invention is applied, is indicated as a whole by the reference character A. and comprises in general a crankcase III, to which 1s secured a plurality of cylinders II. These cylinders II are secured in any suitable manner to the engine crankcase, and a' cylinder head structure I2, which carries suitable valve guides I3, is secured to the cylinder structure in a conventional manner. These valve guides I3 support intake and exhaust valves I4 and I5 respectively, which are preferably moved axially inwardly of the cylinder. The cylinder head structure has formed integrally therewith a rocker box structure llisometimes designated as a housing structure for supporting the valve actuating mechanism. The valves Il and I5 have stem portions I8 projecting into the rocker box I6 which may be actuated by any suitable form of mechanism and said valves are yieldingly closed on the valve seats by the valve springs I9. The cylinder head structure also includes a combustion chamber 20, the cylinder head structure including a wall 2|, which carries the said valve seats 22 and which overlies the open end of the cylinder II. Y I

The present engine is of the air cooled type and the cylinder is provided with suitable n's for dissipating heat produced by the combustion of gases within the cylinder; The cylinder head carries a plurality of cooling fins 23 which extend substantially around the combustion chamber or it might be said that they substantially encircle the cylinder. The ,cylinder head has intake and exhaust passages 24 and 25 associated with the intake and exhaust valves I4 and I5, and each of these passages is so arranged as to be fdrmed within the cylinder head structure and bounded by Wall portions 26 having cooling ns which substantially encircle same.

In most cases itis preferable to have anadditional n area associated with the exhaust valve. and exhaust passage 25 in order to provide adequate'cooling for the exhaust valve guide. In the present construction the cylinder head is provided with an air tunnel 21 which is extended through the cylinder head structure, which tunas at 29a.

chamber for obtaining a maximum dissipation of heat. It is found desirable to provide cooling iins 2B which project upwardly from wall 2| and extend longitudinally of the air tunnel in order to provide an adequate fin area for dissipating heat. It will also be noted that the iins 29 substantially encircle the exhaust valve and exhaust passage 25, and these ns project into the tunnel It will be noted that these fins 29a project inwardly of the tunnel and are contained in planes extending substantially normal to the valve axes whereas the fins 28 lie in planes extending substantially parallel to the valve axes.

It may be further noted that the tunnel 21 extends intermediate the rocker box portion of the cylinder head and the ceiling 2| of the combustion chamber 20. It will thus be seen that there -is provided an air tunnel through the cyl- .inder head structure which supports the engine intake and exhaust valves. This type of engine is generally referred to as an overhead valve engine, because the valves are actuated by valve mechanism from a point overlying the open end of the cylinder. In L-head engines the valves are not exposed to such critical temperatures and they are, furthermore, placed where eiective cooling may be conveniently had. In an overl,

head valve engine the valves are not so con'- veniently located, and it is found that an air tunnel substantially as shown in the present application provides a maximum of cooling areas for dissipating heat. absorbed by the cylinder hgad from the combustion of gases in the comb stion chamber, and thus the improved cooling arrangement as herein described, provides for more eiliecient engine operation and has resulted l in much improved engine performance over those j heretofore produced.

It will be observed that the air tunnel trated in the accompanying drawings, is preferably constructed substantially rectangular in cross-section and thus a considerable portion of the cylinder head wall 2 I, that forms the ceiling of the com-bustion chamber 20, is exposed to the cooling influence of the air flowing through the air tunnel. The central portion of the wall 2|, indicated by the reference character 2|a is .substantially the yhottest stressed portion of the entire cylinder head. This wall 2| also supports the valve seats 22 and if not adequately cooled,

the valve seats will tend to become distorted. It y lwill be noted that the base of the iins 2l are.

portion 2|a and` closely adjacent to this wall serve to dissipate a maximum of heat from theexhaust valve guide is exposed to thecooling in fluences of the air stream flowing through the air tunnel 21. It will be noted thatithe wall Ml is of 'volume of air into direct heat transference relation to interior portions ofthe cylinder head structure and has proved quite advantageous in that this construction has resulted in improved engine performance.

It has been determined that the cooling of the interior portions of the cylinder head may be most efliciently obtained with an air tunnel having a minimum cross-sectional area of from oneflfth W5) to one-fifteenth (M5) the area of the cylinder bore. The construction illustrated in Fig. 1 shows an air tunnel whose cross-sectional area within the iin at the narrowest part, in plane A- A is approximately one-tenth (116) the area of the cylinder bore. The construction illustrated in Fig. 4 shows'flns 28a, which extend relatively higher and quite close to the bottom wall 30 of the rocker box, and has an effective cross-sectional area which is approximately oneflfth (1/5) the area of the cylinder bore.

It will be evident that maximum engine eiliciency is obtained by constructing an air tunnel Whose shape and size is such as to eiect a substantially direct heat transfer from critical areas or parts such as the exhaust valve guide and the central wall portion 2|a of the combustion chamber. A relatively small air flow is of very little practical use, and the proportions I havey set forth above have proved to be adequate and ,to result in much improved engine performance.

defining a combustion chamber overlying the cylinder and a rocker box overlying the combustion chamber, overhead intake and exhaust valves supported by said cylinder head and opening axially inwardly of the cylinder and including valve stems projecting into the interior of A said rocker box, valve actuating mechanism supported in said rocker box, said cylinder head having intake and exhaust passages terminating'respectively in intake and exhaust ports opening into' said-combustion chamber, and an air tunnel extending across the central portion ofthe cylinder intermediate the rocker-.box andvcombustion chamber and overlying a portion. of said intake and exhaust ports,4 said.v cylinder head having valve j guide bores supportingfvalve guidesjiwhich support said valves,` said tunnel constructedto proa minimum practical thickness, and separates the exhaust valveguide I3 from the air tunnel,,

and that this -relatively thin wall 40 extendsalong substantially the entire axial lengthl ofsaid valve guide. The flns 29a within theitunnel 21 serve to dissipate heat from the exhaust passage i ,v

and the exhaust valve guide I3 the temperature of the metal.

thereby lowering y',

The presentair .vide a wall of minimum thickness-substantially parallel to said exhaust valve guide and for substantially the whole'length of said exhaust valve guide bore, and a plurality of cooling Vns lying in planes extending normal to the cylinder and valve axes, encircling said exhaust v.passage and .carried around said vwall portion separating the exhaust valve guide `from the air tunnel.

2.'In an internal combustion engine having a cylinder, a cylinder head structure overlying the cylinder and constructed of an integral stmoture defining a combustion ychamber overlying from the scope of the ,ap-

the cylinder and a rocker box overlying the combustion chamber, overhead intake and exhaust valves supported by said cylinder head and opening axially inwardly of the cylinder and including valve stems projecting into the interior of said rocker box, valve actuating mechanism supported in said rocker box, said cylinder head having intake and exhaust passages terminating respectively in intake and exhaust ports opening into said combustion chamber, and an air tunnel extending across the central portion of the cylinder intermediate the rocker box and combustion chamber and overlying a portion of said intake and exhaust ports, and a plurality of ns carried by said cylinder head and including flns extending into said tunnel from the wall overlying the combustion chamber in planes extend` cylinder, a cylinder head structure overlying the cylinder and cooperating therewith to dene a combustion chamber, intake and exhaust valves supported by said cylinder head and opening axially inwardly of the cylinder, said cylinder head having valve guide bores supporting intake and exhaust valve guides, said cylinder head provided with a substantially rectangular air tunnel open at both ends and extending between said valves and across the central portion of said combustion chamber substantially normal to the cylinder axis, said air tunnel constructed and arranged to provide a side wall section adiacent to said exhaust valve guide bore, the aforesaid side wall section extending substantially parallel with respect to said exhaust valve guide bore and constructed with a minimum thickness for substantially the entire length of the exhaust valve guide bore whereby to place substantially the total length of said exhaust valve guide bore in direct heat transference relation to the air stream flowing through said air tunnel.

CARL F. BACHLE. 

